Ratio of red cars to blue cars in the parking lot was 5 to 3 if there are 40 red cars how many blue cars are there

Which recursive formula can be used to determine the total amount of money earned in any year based on the amount earned in the previous year? f(n+1)=f(n)+5

I’ve been trying all day to figure this puzzle out. i need the work for it aswell. it is a factoring polynomials tarsia. the image is below.

Solve the equation for b: a= (1/2)(b)(h)